The present invention relates to a method and an apparatus for measuring an injection amount of a fuel injector so as to allow high precision measurement of a small flow of a liquid, such as fuel for an engine, injected from an electromagnetic fuel injector.
In order to measure the injection amount of an electromagnetic fuel injector, fuel set under a pressure high enough for injection is supplied to the fuel injector. A predetermined number of, for example 1,000, injection drive pulses are supplied to the injector and fuel injected by the fuel injector is collected in a measuring cylinder. The amount of fuel collected in this manner is measured visually or with a scale. The average injected amount per injection operation, for example, is calculated from the amount of the collected and measured amount of injected fuel.
However, the injected amount per injection operation of such a fuel injector is as small as 0.001 to 0.1 cc (about 0.7 to 70 mg). Moreover, the injection period is also as small as 10 to 100 msec under normal engine conditions. For these reasons, it is almost impossible to measure the injection amount of fuel per injection operation of a fuel injector considering the response time (more than 1 sec) and the resolution (10 mg). The scale for measuring the collected fuel is subject to the effects of vibration or air flow at the installed location, and is poor in measuring precision even for 1,000 injection operations.